ng persistence once and for all in a reusable (system) library providing the class of persistent predicates. The main e#ect of declaring a predicate persistent (a process for which we propose a suitable syntax, compatible with the Ciao system's assertion language) is that any changes made to such predicates persist from one execution to the next one, and are transactional, and, optionally, externally visible. The model allows associating an external, persistent storage medium (a file, a database table, etc.) to each such predicate, which will "reside" in that medium. Notably, persistent predicates appear to a program as ordinary (dynamic) predicates: calls to them do not need to be coded or marked specially, and the builtins to update them are (suitably modified versions of) the same used with the internal database (e.g., asserta/1, assertz/1, retract/1, etc.). Thus, only minor modifications to the program code (often independent of its internal logic) are needed to achieve persistence